The present invention relates to digital video systems, and more particularly, to circuits for reducing the hardware required in such systems.
In digital broadcast systems, the effective use of the data rate is of primary importance. A reduction in data rate reduces both video tape usage and the necessary transmission bandwidth; however, this must be accomplished while maintaining broadcast quality pictures.
One method of data rate reduction which is presently under consideration is the process of sub-Nyquist sampling, such as is disclosed in the paper "Sub-Nyquist Encoded PCM NTSC Color Television" by John P. Rossi in the book "Digital Video", a review of SMPTE papers, and in the article by Leonard S. Golding, "Frequency Interleaved Sampling of a Color Television Signal", IEEE Transactions on Communication Technology, Volume COM-19, page 972, December 1971. These sub-Nyquist type systems have samples with the diagonal distance between the samples being greater than the horizontal distance between the samples. Since the smaller the distance between samples the greater the resolution, these systems are capable of increasing the horizontal resolution which is available at a given data rate, but at the expense of the diagonal resolution.
A system for overcoming this disadvantage is shown in U.S. patent application Ser. No. 132,137, filed March 20, 1980, (RCA 74,547), now abandoned in favor of continuation application Ser. No. 168,077, filed July 14, 1980 (RCA 74,547A), both entitled "Data Rate Reduction For Digital Video Signals By Subsampling And Adaptive Reconstruction." The method of said applications comprises dividing a signal into first and second time portions, transmitting the first portion, and transmitting a control signal adapted to control the reconstruction of said second portion from the transmitted first portion. However, the embodiment of the invention of said prior applications may require a large amount of circuitry.
It is therefore desired to reduce the amount of hardware in a Digital Video System.